Various kinds of defects in semiconductor circuits, due to, e.g., pipes, ionic contamination and photolithography, that cause low level leakage are a major cause of circuit failures when these circuits are used in the field. Such defects have not been readily identifiable during normal testing of the circuits after manufacture.
Known testing methods for identifying some defects in semiconductor circuits and structures irradiate light of a given intensity or utilize heat to induce leakage in the circuits, as, e.g., described in commonly assigned U.S. Pat. No. 4,015,203, filed on Dec. 31, 1975, by R. L. Verkuil, and in U.S. Pat. No. 4,004,222, filed on Nov. 20, 1974, by R. E. Gebhard. Also, commonly assigned U.S. Pat. No. 3,795,859, filed on July 3, 1972, by J. F. Benante, N. M. Donofrio and R. H. Linton, discloses a testing technique wherein conventional or normal levels of operating voltages are used to test or determine the characteristics of the circuits or devices.